1. Technical Field
This application relates to a rotational thrombectomy wire for clearing thrombus from native vessels.
2. Background of Related Art
In one method of hemodialysis, dialysis grafts, typically of PTFE, are implanted under the patient's skin, e.g. the patient's forearm, and sutured at one end to the vein for outflow and at the other end to the artery for inflow. The graft functions as a shunt creating high blood flow from the artery to the vein and enables access to the patient's blood without having to directly puncture the vein. (Repeated puncture of the vein could eventually damage the vein and cause blood clots, resulting in vein failure.) One needle is inserted into the graft to withdraw blood from the patient for transport to a dialysis machine (kidney machine); the other needle is inserted into the graft to return the filtered blood from the dialysis machine to the patient. In the dialysis machine, toxins and other waste products diffuse through a semi-permeable membrane into a dialysis fluid closely matching the chemical composition of the blood. The filtered blood, i.e. with the waste products removed, is then returned to the patient's body.
Over a period of time, thrombus or clots may form in the graft. Thrombus or clots may also form in the vessel. One approach to break up these clots and other obstructions in the graft and vessel is the injection of thrombolytic agents. The disadvantages of these agents are they are expensive, require lengthier hospital procedures and create risks of drug toxicity and bleeding complications as the clots are broken.
U.S. Pat. No. 5,766,191 provides another approach to breaking up clots and obstructions via a mechanical thrombectomy device. The patent discloses a basket having six memory wires expandable to press against the inner lumen to conform to the size and shape of the lumen. This device could be traumatic if used in the vessel, could denude endothelium, create vessel spasms and the basket and drive shaft could fracture.
U.S. Pat. No. 6,090,118 discloses a mechanical thrombectomy device for breaking up clots. The single thrombectomy wire is rotated to create a standing wave to break-up or macerate thrombus. U.S. Patent Publication No. 2002/0173812 discloses another example of a rotational thrombectomy wire for breaking up clots. The thrombectomy wire has a sinuous shape at its distal end and is contained within a sheath in a substantially straight non-deployed position. When the sheath is retracted, the distal portion of the wire is exposed to enable the wire to return to its non-linear sinuous configuration. The wire is composed of stainless steel. Actuation of the motor causes rotational movement of the wire, creating a wave pattern, to macerate thrombus. The device of the '812 patent publication is effective in atraumatically and effectively breaking up blood clots in the graft and is currently being marketed by Datascope, Inc. as the Pro-Lumen* thrombectomy catheter. In the marketed device, the wire is a bifilar wire, composed of two stainless steel wires wound side by side with a metal tip and an elastomeric tip at the distalmost end.
Although the sinuous wire of the '812 publication is effective in proper clinical use to macerate thrombus in dialysis grafts, it is not suited for use in native vessels. The device is indicated for use in grafts, and if improperly used the wire can kink or knot, and perhaps even break. The wire can also bend, making it difficult to withdraw after use, and can lose its shape. Additionally, the wire would be abrasive to the vessel and the vessel could get caught in the interstices of the wire. It could also cause vessels spasms which can cause the vessel to squeeze down on the wire which could break the wire. Similar problems would occur with the use of the device of the '118 patent in native vessels.
The need therefore exists for a rotational thrombectomy wire which can be used to clear clots or other obstructions from the native vessels. Such wire could advantageously be used not only in native vessels adjacent dialysis grafts but for deep vein thrombosis and pulmonary embolisms.